The invention relates to a regenerating photoelectrochemical cell and, more particularly, to a cell of this type that does not absorb, or that very weakly absorbs electromagnetic radiation having wavelengths in the visible range. The term regenerating photoelectrochemical cell is generally understood to mean an electrochemical system in which the reactions at the electrodes are reversible and in which the different types of chemicals involved are preserved.
Regenerating photoelectrochemical cells of the semiconductor oxide/electrolyte interface type are already known. In these cells, the semiconductor oxide is deposited in the form of a continuous layer on a substrate previously covered with an electrode. However, the disadvantage of these cells is that they only absorb a very small proportion of the incident light, with the result that their efficiency is too low to produce a utilizable amount of energy.
PCT International Patent Application WO 91/16719 discloses a regenerating photoelectrochemical cell having a titanium dioxide layer which is produced in the form of a porous nanostructure formed of sintered colloidal particles and covered with a monomolecular layer of chromophors. Although providing a high efficiency, this cell nonetheless has the disadvantage that it absorbs a large amount of the incident light with wavelengths in the visible and ultraviolet regions. There are, however, numerous applications for which it is preferable or even essential that the cell does not absorb light in the visible range.
European patent EP 407 182 describes a photoelectrochemical cell comprising, among others, a porous membrane of semiconductor oxide formed of sintered colloidal particles and having no chromophors. The efficiency of a cell of this type is, however, not entirely satisfactory.